| 1. |
- Nejadmoghadam, Elham, 1984, et al.
(author)
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Stabilization of bio-oil from simulated pyrolysis oil using sulfided NiMo/Al 2 O 3 catalyst
- 2023
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In: Fuel. - 0016-2361. ; 353
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Journal article (peer-reviewed)abstract
- Pyrolysis oil comprises compounds with a broad range of functional groups making its thermal/catalytic upgrading challenging due to the formation of undesired char. In this context, the current contribution addresses the thermal and catalytic hydrotreatment of a simulated pyrolysis oil containing all the representative groups of compounds under bio-oil stabilization conditions (180–300 °C, 60 bar, 4 h) using sulfided NiMo/Al2O3. The effect of reaction conditions and different oxygenated organic compounds on the yields and properties of products was compared thoroughly. Interestingly, a correlation between the presence/absence of oxygenated furan and sugar compounds was found to significantly affect the yield of liquid product containing stabilized compounds. The presence of such compound groups significantly enhances the solid formation via oligomerization and polymerization reactions. To gain further insight, the solid products were analyzed/characterized in detail to elucidate their characteristics by extracting them into a dimethyl sulfoxide (DMSO) soluble and insoluble solid fraction. It was found that in the presence of NiMo/Al2O3, increasing temperature from 180 to 300 °C enhances the formation of liquid product due to transformation of some of the soluble solids, while for experiments without the catalyst, the formation of solids was significantly higher. Oppositely, during heating up to 180 °C, no solids were found in the case without the catalyst, however the presence of the catalyst during heating resulted in solid formation due to various catalytic reactions that promoted char formation. Analysis of solids revealed that the structure of soluble solids at lower temperatures (180 °C) using the catalyst was closely related to sugar derivatives, whereas the corresponding insoluble solids with higher molecular weight were not fully char-like developed. However, at higher temperatures, the soluble and insoluble solid compositions were found to contain aliphatic compounds and fully developed char, respectively. Therefore, the stabilization of furan particularly with attached carbonyl groups and sugars derivatives in pyrolysis oil is of great importance to improve upgrading efficiency.
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| 2. |
- Nejadmoghadam, Elham, 1984, et al.
(author)
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Stabilization of fresh and aged simulated pyrolysis oil through mild hydrotreatment using noble metal catalysts
- 2024
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In: Energy Conversion and Management. - 0196-8904. ; 313
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Journal article (peer-reviewed)abstract
- The nature and reactivity of the oxygenates, containing different functional chemical groups, and especially carbonyl compounds, render pyrolysis oil unstable. Alterations in physical and chemical properties of pyrolysis oil during storage and the catalytic stabilization of this oil is therefore critical and is the objective of the current work. In this study, Pd/Al2O3, Pt/Al2O3, Rh/Al2O3, Re/Al2O3 and sulphided NiMo/Al2O3 catalysts were employed in the hydrotreatment (180 °C, 60 bar H2, 4 h) of simulated pyrolysis oil to examine their effect on stabilization and potential polymerization routes. Of all the catalysts used, Pd/Al2O3 with well-dispersed metal particles, and a high char-suppressing potential was the most effective catalyst. It had the highest bio-liquid yield and the highest selectivity to low molecular weight stabilized oxygenates and deoxygenated products. In addition, the acidity in the light fraction was low and a very low solid product formation was found that consisted mainly of soluble polymers composed predominantly of aliphatic compounds and sugars, whereas insoluble polymers were not fully developed char. The solid yield increased in the following order: Pd (3.3 wt%) < Rh (13.3 wt%) < NiMo (13.6 wt%) < Pt (21.5 wt%) < Re (25.8 wt%) < Blank (27.4 wt%). This trend was also accompanied by an enhanced yield of heavy oligomers in the corresponding liquid phase abundant in phenolic compounds compared to carboxylic acids and aliphatic compounds based on GPC and P-NMR analyses. The Pd loading necessary to obtain a high-quality product was also assessed, and the lower carbon loss when using catalysts with smaller contents of metal was revealed. Based on the results a detailed reaction network was proposed regarding the reactions during stabilization of sugars, aldehydes, ketones, furans, acids and phenols present in pyrolysis oil. To delve deeper into the simulated pyrolysis oil properties, it was subjected to accelerated aging. Interestingly as much as 79 % of the feed was converted during aging. According to GC/MS analysis only large oligomers were formed that could not be detected. When removing the most reactive components from the feed, i.e. the sugar and furan, the conversion was lowered to 53 %. Catalytic stabilization was conducted on the aged oil and compared with stabilization followed by aging. The results showed that the solid formation increased from 5.1 to 9.1 % when the pyrolysis oil was first aged, followed by stabilization. A suggested reason for this is the large amount of oligomers that were formed during the aging. Thus, aging before stabilization is very negative for an industrial process.
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| 3. |
- Nejadmoghadam, Elham, 1984
(author)
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Study of bio-oil and bio-char production from thermal and catalytic hydrotreatment of simulated pyrolysis oil under mild conditions
- 2023
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Licentiate thesis (other academic/artistic)abstract
- Pyrolysis oil derived from fast pyrolysis of lignocellulosic biomass is a promising alternative energy source used to produce renewable biofuels. However, the high reactivity of unsaturated oxygenated compounds in pyrolysis oil results in charring and deactivation of the catalyst under severe hydrotreatment conditions. This thesis focuses on reactions during stabilization of such oils, specifically, the undesirable carbon loss to solid char as the main side reaction. In the first study, mild thermal and catalytic hydrotreatment of a simulated pyrolysis oil, containing a comprehensive mixture of various oxygenated groups, was performed using NiMo/Al2O3 under mild conditions of 180-300°C and 60 bar hydrogen in a batch reactor. The solid products were extracted into soluble and insoluble solid fractions to determine the degree of polymerization. It was found that the soluble solids transformed into the bio-liquid product and solid insoluble yield was suppressed at elevated temperatures. It was also accompanied by a higher degree of hydrodeoxygenation (HDO) causing the stabilization of light oxygenates, and a significant decrease in the formation of heavy oligomers in the liquid phase. In catalyst-free experiments, the formation of solids was higher and showed a decreasing trend when increasing the temperature, except during heating where no solids were observed for the non-catalytic experiment. In the presence of the catalyst, the soluble solids at lower temperatures (180°C) consisted of macromolecule structures that were rich in sugar derivatives, while the corresponding insoluble solids were not fully developed into char. Their composition changed to aliphatic compounds and fully developed char respectively at higher temperatures. Moreover, the removal of furan and sugar compounds was found to be crucial to reduce the solid char formation. In the second study, a set of catalysts; Pt/Al2O3, Rh/Al2O3, Pd/Al2O3, Re/Al2O3, and NiMo-S/Al2O3 was used to stabilize the same simulated pyrolysis oil at identical reaction conditions (180°C) as applied in the first study. The catalyst screening results showed that Pd/Al2O3 was significantly better in terms of achieving the highest conversion of pyrolysis oil and producing a high yield (66 wt%) of liquid oil product. The bio-liquid was mostly composed of low molecular weight compounds such as stabilized oxygenates and hydrocarbons. It also featured a minimum solid formation (3.3 wt%) in which soluble polymers were more pronounced. The results also indicated that NiMo-S/Al2O3 was fairly good in catalyzing reactive compounds, except furans, into stable light oxygenates with the formed solids rich in heavy insoluble polymers (13.6 wt%). The Rh/Al2O3 was comparable to NiMo-S/Al2O3, however, Pt/Al2O3 and particularly Re/Al2O3 rendered poor performances with the lowest yields and qualities of the liquid products, consisting mainly of heavy soluble oligomers, which resulted in a high degree of polymerization.
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| 4. |
- Raouf, Morassa, et al.
(author)
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A favored CO2 separation over light gases using mixed matrix membrane comprising polysulfone/polyethylene glycol and graphene hydroxyl nanoparticles
- 2020
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In: Process Safety and Environmental Protection: Transactions of the Institution of Chemical Engineers, Part B. - : Elsevier BV. - 1744-3598 .- 0957-5820. ; 133, s. 394-407
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Journal article (peer-reviewed)abstract
- A novel polysulfone (PSF) mixed matrix membrane blended by polyethylene glycol (5 and 10 wt.%) was synthesized in which the graphene hydroxyl (G-OH) nanoparticles incorporated. Polyethelene glycol (PEG) as an affordable additive provides a proper CO2 affinity. Moreover, the G-OH nanoparticles was enhanced the CO2 permeability in MMMs through Lewis acid- base interaction between electron withdrawing oxygen of -OH and CO2. First, PSF membrane was modified via adding PEG. Obtained results were shown that the CO2 permeability increased significantly from 15.9 Barrer (for neat PSF) to 28.2 Barrer (for PSF/PEG (10 wt%), while a fairly significant increase in CO2/CH4 selectivity (from 12.23 forneat PSF to 12.81 for PSF/PEG (10 wt%) at the pressure of 2 bar and temperature of 35 degrees C. Second, the G-OH nanoparticles were incorporated (1, 2, 3, 4 and 5 wt%) into the both PSF/PEG (5 wt%) and PSF/PEG(10 wt%) matrix to prepare the PSF/PEG/G-OH MMMs. Results showed the best CO2/CH4 selectivity was obtained at 5 wt% loading of G-OH for both PSF/PEG (5 wt%) and PSF/PEG (10 wt%) were 20.94 and 22.39, respectively; at pressure of 8 bar. The separation properties of membranes were also evaluated at higherfeed pressure and the obtained results were discussed. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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| 5. |
- Salam, Muhammad Abdus, 1983, et al.
(author)
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Elucidating the role of NiMoS-USY during the hydrotreatment of Kraft lignin
- 2022
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 442
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Journal article (peer-reviewed)abstract
- Major hurdles in Kraft lignin valorization require selective cleavage of etheric and C–C linkages and subsequent stabilization of the fragments to suppress repolymerization reactions to yield higher monomeric fractions. In this regard, we report the development of efficient NiMo sulfides and ultra-stable Y zeolites for the reductive liquefaction and hydrodeoxygenation of Kraft lignin in a Parr autoclave reactor at 400 °C and 35 bar of H2 (@25 °C). Comparing the activity test without/with catalyst, it is revealed that NiMo sulfides over ultra-stable Y zeolites (silica/alumina = 30) achieved a significant reduction (∼50 %) of the re-polymerized solid residue fraction leading to a detectable liquid product yield of 30.5 wt% with a notable monocyclic and alkylbenzenes selectivity (∼61 wt%). A physical mixture counterpart, consisting of hydrothermally synthesized unsupported NiMoS and Y30, on the other hand, shows lower selectivity for such fractions but higher stabilization of the lignin fragments due to enhanced access to the active sites. Moreover, an extended reaction time with higher catalyst loading of the impregnated NiMoY30 facilitated a remarkable alkylbenzene (72 wt%) selectivity with an increased liquid yield of 38.9 wt% and a reduced solid residue of 16.4 wt%. The reason for the high yield and selectivity over NiMoY30, according to the catalyst characterization (H2-TPR, XPS, TEM) can be ascribed to enhanced stabilization of depolymerized fragments via H2-activation at a lower temperature and high hydrodeoxygenation ability. In addition, the better proximity of the acidic and deoxygenation sites in NiMoY30 was beneficial for suppressing the formation of polycyclic aromatics.
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| 6. |
- Salam, Muhammad Abdus, 1983, et al.
(author)
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One-pot reductive liquefaction of sawdust to renewables over MoO x -Al 2 O 3 variants: insight into structure-activity relationships
- 2024
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In: Sustainable Energy and Fuels. - 2398-4902. ; 8:12, s. 2668-2681
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Journal article (peer-reviewed)abstract
- Valorization of forest residual products can offer a vital pathway to derive bio-based chemicals and fuel components. Herein, we report the effective and direct conversion of sawdust biomass over a supported Mo-oxide catalyst that results in a dominant fraction of aliphatic/cyclic alkanes and alkylbenzenes with low residual solids. The reductive liquefaction was conducted in an autoclave reactor using a series of MoOx-Al2O3 variants in the range of 340-400 °C with an initial H2 pressure of 35 bar for 4 h. At 340 °C, a correlation between Mo-loadings and reactivity for depolymerization and hydrodeoxygenation was found optimal for a surface density of 3.2 Mo-atoms per nm2 corresponding to 8 wt% Mo-loading. The liquefied fraction showed high selectivity (∼38%) for the formation of cycloalkanes and alkylbenzenes. At higher temperatures (400 °C) enhanced reactivity over the optimal catalyst showed higher cycloalkane and alkylbenzenes formation (∼57%) at a low biomass-to-catalyst feed mass ratio (3 : 1). At a higher ratio (10 : 1), alkylphenols (∼41%) are the leading product fraction followed by cycloalkanes and alkylbenzenes (∼34%) with a high liquefied monomer bio-oil product yield of 39.4 wt%. Catalyst characterization via XRD, Raman, H2-TPR, and XPS analysis revealed that the origin for this reactivity arises from the Mo species formed and stabilized over the support surface. A well dispersed, octahedral, higher fraction of easily reducible Mo-species (Mo5+) was evident over the optimal catalyst which enables enhanced C-O cleavage facilitating the hydrodeoxygenation reaction. Moreover, the solid residue yield could be reduced to below 5 wt% by optimizing the reaction conditions and particle size of the sawdust.
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